Germany's leading economic think tanks on Thursday raised their growth forecast for Europe's top economy this year and next year, but warned of headwinds from new government policies. The four institutes -- Ifo in Munich, DIW in Berlin, IW in Halle and RWI in Essen -- predicted that German gross domestic product (GDP) would expand by 1.9 percent in 2014, up from 0.4 percent in 2013, and then grow by 2.0 percent in 2015.